1. Field of the Invention
This invention relates to disk drive suspensions, and more particularly to wireless disk drive suspension assemblies having a flexible conductive laminate forming the electrical connection between the slider, including the disk read element/head, and the suspension signal electronics. In a particular aspect, the invention provides an improved shunt for protecting the read head during suspension assembly operations. The shunt structure is reusable and comprises a conductive material having a resealable adhesive. The shunt structure connects the flexible conductive laminate leads so as to redirect electrostatic discharge currents away from the read head. In a further aspect, the shunt structure may be attached to the proximate contact pads between test operations, or to new contact areas especially designed to take advantage of the invention by remaining attached both between and during testing operations.
2. Related Art
One of the major problems with wireless suspensions is the occurrence of spontaneous electrostatic discharges (ESD) through them when they are connected to magnetoresistive (MR) disk read elements/heads or giant magnetoresistive (GMR) element/heads. Any external charge poses a risk of traveling to the MR or GMR element. Thus a charge from a person or from an insulating surface charge build-up can flow via the trace/wire leads (or pads) to the slider/head and damage the MR sensor element, sometimes melting the sensor element. It takes as little as 15 volts for a GMR head to be damaged. One of the ways to prevent this phenomenon is to connect all the leads in parallel so that this current does not pass through the MR element. Designing a circuit with a shunt across the leads before the head is attached to the suspension will connect the leads in parallel. But, this solution only is effective when the assembly of the wireless conductor and MR or GMR is in other than a test or operating condition. In a test or operating situation, after the head/element is attached to the conductors/traces to be tested for reading and writing to disk, the presence of the shunt circuitry prevents testing and the shunt needs to be removed. The shunt is cut-off from the remainder of the circuit and it cannot be reattached; electrostatic discharge protection no longer exists for the affected part although more handling and testing is required.
It is an object of the invention to provide method and apparatus for continuing shunt protection of wireless suspension assemblies. It is another object to provide a novel shunt structure that is readily attached to and detached from the contact pads or other exposed areas of the conductive traces of the flexible conductive laminate portion of the wireless suspension for use as needed to protect the MR and GMR elements/heads. It is a further object to provide a conductive web that will connect the conductive traces in parallel, and adhesive allowing the separable attachment of the web to the traces. It is a still further object to provide a metal or metal deposited conductive web with varying geometries of conductive areas and adhesive areas. Yet another object is to provide conductive web attachment to the proximate contact pads of the suspension, to be removed during testing and left on during assembly and between tests to nearly continually protect the head magnetoresistive element. A further object is to provide continuous ESD protection for the MR and GMR element attached to a flexible conductive circuit by providing conductive web attachment to the traces beyond the contact pads such that the web is left in place during suspension assembly, during testing and between tests.
These and other objects of the invention to become apparent hereinafter are realized in the method of protecting a disk read head from spontaneous electrostatic discharge current during the assembly but not during the actual testing operations of a disk drive suspension comprising a load beam and a flexible conductive laminate, the laminate having at least one pair of trace conductors connected to the magnetoresistive read head, including exposing adjacent portions of the trace conductors comprising each conductor pair, and applying to the exposed trace conductor portions a separably adherent shunt structure to temporarily connect each the pair of trace conductors in parallel while there is a potential for a spontaneous electrostatic discharge current reaching the disk read head, such that the discharge currents are directed away from the head.
In an alternative embodiment, the invention provides the method of protecting a disk read head from spontaneous electrostatic discharge current during the assembly and during actual testing operations of a disk drive suspension comprising a load beam having a base and a flexible conductive laminate, the laminate having at least one pair trace conductors connected to the disk read head and to a first series of contact pads adjacent the load beam base useful for attaching test leads, including maintaining a second series of contact pads electrically connected to the trace conductors between the first series of contact pads and the disk read head and exposed, and applying to the second series of contact pads a shunt structure separably adherent to the laminate and connecting the trace conductors in parallel through the second series of contact pads during assembly and testing of the suspension with test leads attached to the first series of contact pads and there is a potential for a spontaneous electrostatic discharge current reaching the disk read head, such that the discharge currents are directed away from the disk read head.
In these and like embodiments, typically, the method further includes forming the flexible conductive laminate from a dielectric plastic layer and one or more pairs of conductive traces supported by the dielectric plastic layer in insulated relation, forming the flexible conductive laminate from a base metal layer, a dielectric plastic layer and one or more pairs of conductive traces supported by the metal base layer and the dielectric plastic layer in insulated relation, forming the shunt structure from a conductive web and an adhesive bonded to the web and separably bondable to the laminate with the conductive web in conducting relation with the trace conductor portions, selecting as the conductive web a conductive metal sheet, selecting as the conductive metal sheet a flexible sheet of copper, silver or gold, distributing the adhesive across the web in separate, discrete quantities, forming the adhesive into separated flat spots of adhesive for separably adhering the web to the laminate, forming the adhesive into separated dimples of adhesive for separably adhering the web to the laminate, selecting as the conductive web a nonconductive plastic sheet material having a conductive deposit of metal thereon, forming the conductive metal deposit with raised portions for trace conductor contact, locating the conductive metal deposit in a predetermined location on the plastic sheet material, and forming areas of adhesive adjacent the metal deposit for separably bonding the sheet material to the laminate with its conductive metal deposit in shunting conductive contact with the exposed trace conductor portions, defining discrete dimples of adhesive across the conductive metal deposit for separably adhering the sheet to the laminate, defining flat spots of adhesive across the conductive metal for separably adhering the sheet to the laminate, forming the shunt structure from a nonconductive web, a conductor material distributively disposed on the web, and an adhesive separably bondable to the laminate with the conductor material in conducting contact with the trace conductor portions, selecting as the nonconductive web a plastic sheet material, distributing the conductor material in a pattern across the plastic sheet material web and distributing the adhesive in a further pattern across the plastic sheet material web for adhering the web to the laminate, defining a grid of conductor metal, attaching the conductor metal grid to the plastic sheet material, and arranging the adhesive to separably bond the web to the laminate between the elements of the grid, the grid elements electrically contacting the trace conductor portions, defining a three dimensional sheet of conductive material, attaching the conductive material sheet to the plastic sheet material, and arranging the adhesive to separably bond the web to the laminate with the conductive material sheet in electrical contact with the trace conductor portions, and/or defining a distributed series of raised areas on the conductive material sheet to provide the material the third dimension, the raised areas being arranged to make electrical contact with the trace conductor portions.
The method also further typically includes selecting as the conductive web a nonconductive plastic sheet material having a conductive deposit of metal thereon, forming the conductive metal deposit with raised portions for trace conductor contact through the second series of contact pads, locating the conductive metal deposit in a predetermined location on the plastic sheet material, and forming areas of adhesive adjacent the metal deposit for separably bonding the sheet material to the laminate with its conductive metal deposit in shunting conductive contact with the exposed second series of contact pads, forming the shunt structure from a nonconductive web, a conductor material distributively disposed on the web, and an adhesive separably bondable to the laminate with the conductor material in conducting contact with the trace conductor portions through the second series of contact pads.
The invention apparatus comprises in one embodiment a disk drive suspension shunt structure for connecting in parallel a pair of trace conductors in a flexible conductive laminate connected to a disk read head, the trace conductors having exposed portions, the shunt structure comprising a flexible carrier, an adhesive carried on the carrier, the adhesive being separably adherent to the laminate, and a conductor material distributed across the carrier and relative to the adhesive such that the conductive element electrically connects in parallel the trace conductors at their exposed portions in the adhered condition of the carrier to the laminate.
In a further embodiment the invention provides a disk drive suspension comprising a load beam, a disk read head, a flexible conductive laminate comprising a plastic layer containing conductive traces electrically connected to the head in a manner potentially subjecting the head to spontaneous electrostatic discharge currents deleterious to the head, the trace conductors having adjacent exposed portions, and a shunt structure comprising a web adapted and arranged to electrically connect the laminate conductive traces at their the exposed portions, and an adhesive on the web separably bonding the shunt structure to the laminate in electrically connected relation with the conductive traces, whereby the discharge currents are directed away from the disk read head.
In these and like embodiments, typically, the flexible conductive laminate comprises a dielectric plastic layer and one or more pairs of conductive traces supported by the dielectric plastic layer in insulated relation, the flexible conductive laminate comprises a base metal layer, a dielectric plastic layer and one or more pairs of conductive traces supported by the metal base layer and the dielectric plastic layer in insulated relation, the shunt structure web comprises a conductive metal sheet, the conductive metal sheet comprises a flexible sheet of copper, silver or gold, the adhesive is distributed across the web in separate, discrete quantities, the adhesive is formed into separated flat spots for separably adhering the web to the laminate, the adhesive is formed into separated dimples of adhesive for separably adhering the web to the laminate, the web comprises a nonconductive plastic sheet material having a conductive deposit of metal thereon, the conductive metal deposit is formed with raised portions for trace conductor contact, the conductive metal deposit is located in a predetermined location on the plastic sheet material, and in which areas of adhesive are formed adjacent the metal deposit for separably bonding the sheet material to the laminate with its conductive metal deposit in shunting conductive contact with the exposed trace conductor portions, the adhesive is formed into discrete dimples distributed across the conductive metal deposit for separably adhering the sheet to the laminate, the adhesive is formed into flat spots across the conductive metal deposit for separably adhering the sheet to the laminate, the shunt structure web comprises nonconductive sheet material, a conductor material distributively disposed on the web nonconductive sheet material, and an adhesive separably bondable to the laminate with the conductor material in conducting contact with the trace conductor portions, the nonconductive web comprises a plastic sheet material, the conductor material is distributed in a pattern across the plastic sheet material web and the adhesive is distributed in a further pattern across the plastic sheet material web for adhering the web to the laminate, the conductor material comprises a grid of conductor metal, the conductor metal grid being attached to the plastic sheet material, and the adhesive being arranged to separably bond the web to the laminate between the elements of the grid, the grid elements being in electrical contact with the trace conductor portions, the conductive material comprises a three dimensional sheet, the conductive material sheet being attached to the plastic sheet material, and the adhesive being arranged to separably bond the web to the laminate with the conductive material sheet in electrical contact with the trace conductor portions, and forming a distributed series of raised areas on the conductive material sheet to provide the material sheet its the third dimension, the raised areas being arranged to make electrical contact with the trace conductor portions.
In a further embodiment, the invention provides a disk drive suspension having a disk read head protected from spontaneous electrostatic discharge current during the assembly and testing of the disk drive suspension, the suspension comprising a load beam having a base and a flexible conductive laminate, the laminate having at least one pair trace conductors connected to the disk read head and to a first series of contact pads adjacent the load beam base useful for attaching test leads, a second series of contact pads electrically connected to the trace conductors between the first series of contact pads and the disk read head and exposed, and applied to the second series of contact pads a shunt structure separably adherent to the laminate, the shunt structure connecting the trace conductors in parallel through the second series of contact pads during assembly and testing of the suspension.
In this and like embodiments, typically, the shunt structure is formed from a conductive web and an adhesive bonded to the web and separably bondable to the laminate with the conductive web in conducting relation with the trace conductor portions through the second series of contact pads, and the conductive web comprises a nonconductive plastic sheet material having a conductive deposit of metal thereon.